Carbonic anhydrase IX up-regulation is associated with adverse clinicopathologic and biologic factors in neuroblastomas.

The overexpression of carbonic anhydrase IX, a hypoxia-induced enzyme, is associated with an adverse prognosis in many cancers. However, carbonic anhydrase IX expression in neuroblastoma, the most common extracranial pediatric tumor, has not been reported. Membranous and/or strong cytoplasmic carbonic anhydrase IX expression, assessed by immunohistochemistry, was present in 21 (23%) of 91 neuroblastomas but was absent in ganglioneuromas (n = 9). The proportion of neuroblastomas showing membranous carbonic anhydrase IX expression was higher in neuroblastomas with 1p deletion and MYCN amplification. Nuclear carbonic anhydrase IX expression was seen in less than 10% of ganglion cells in all ganglioneuromas. Of 91 neuroblastomas, 16 (18%) showed nuclear carbonic anhydrase IX expression in 10% or more tumoral cells. The proportion of neuroblastomas showing nuclear carbonic anhydrase IX expression was significantly higher in patients with adverse clinical (increasing stage and high-risk group), pathologic (unfavorable group and high mitosis-karyorrhexis-index), and biologic (MYCN-amplification and 1p deletion) factors. Carbonic anhydrase IX total protein levels, quantified by enzyme-linked immunosorbent assay, were higher in neuroblastomas (n = 49; geometric mean, 0.47 pg/µg; range, 0.0-6.52 pg/µg) than in ganglioneuromas (n = 6; geometric mean, 0.20 pg/µg; range, 0.09-0.47 pg/µg) and were significantly higher in MYCN-amplified neuroblastomas. Nuclear carbonic anhydrase IX expression was associated with a poorer overall survival (P = .003) and event-free survival (P = .004), although the relationships were no longer significant when adjusted for high-risk disease. There was no significant association of membranous carbonic anhydrase IX expression or higher-than-median total protein levels with overall survival or event-free survival. Carbonic anhydrase IX is expressed at significantly higher levels in neuroblastomas from patients with adverse clinicopathologic and biologic factors indicating that it is a biomarker of aggressive disease in neuroblastomas.